This invention relates to a resonator force transducer assembly especially adapted for measuring relatively large forces.
Resonator force transducers consisting typically of either a single or double-bar vibratory elements made of quartz or similar rigid material have been proposed for a variety of uses such as measurement of acceleration, measurement of pressure and in general measurement of any parameter which can be translated into a force. See for example U.S. Pat. Nos. 3,238,789 and 4,215,570. The force measurement is made in such devices by causing the bar or bars to vibrate, applying the forces along the longitudinal axes of the bars, and then determining the change in frequency of vibration of the bars caused by the applied force. This operation is fully described in the two cited references.
The double-bar transducer arrangement is proving especially advantageous because of the high mechanical Q which can be achieved, at least with those which utilize a rigid material such as quartz, and this, in turn, provides high resolution. Also, such transducers provide long term stability and may be easily and reliably fabricated in miniaturized form by photolithographic and chemical etching processes. However, with the increase in resolution and sensitivity and the decrease in size, the magnitude of the forces which can be measured is decreased because of the fragility of the transducer element.